That's why I mentioned multiple addresses. The public addresses (assigned using SLAAC or DHCPv6) are for global reachability, while you use the local prefix for stable addresses within your network.
If you want stable global addresses, you should request an AS number and prefix, and choose a provider that allows you to announce it with BGP.
If you want stable global addresses, you should request an AS number and prefix, and choose a provider that allows you to announce it with BGP.